1. Field of the Invention
The present invention relates to a zoom lens assembly, and more specifically, to a zoom lens assembly adapted for an apparatus capable of projecting or photographing.
2. The Related Art
Due to successive developments on the recent electronic products, especially on a projecting and photographing apparatus, their essential corresponding optical elements have to be raised with great precision in compliance with the requirements of qualities and the optimum image effects. A common character appearing in the above apparatus should have an ability of how to implement optically zooming by using an optical lens. Physically, the lens has a utility of being moveable to carry out zooming in/out of an image. Therefore, made as an essential optical element of the above apparatus, the performance of any image is absolutely depended on whether the fabrication quality of the optical lens is great or not.
Generally speaking, a zoom lens assembly ordinarily comprises a lens system defined with a plurality of optical lenses with different curvatures. Furthermore, the plurality of optical lenses can be divided into at least two lens groups, which are respectively disposed within two corresponding internal barrels for constructing a first and second lens sets. Eventually, the lens sets are allocated within an external holder or an external barrel. Meanwhile, either the external holder or the external barrel insides are shaped suitable for the reciprocal and telescope movements of an internal barrel with respect to the external holder or the external barrel. The zoom lens assembly is consequently provided with a zooming capability. In optical industry, any one of the lens sets has to be kept extremely controlled in a concentric and coaxial manner, even many times during opposite movements between the lens sets, in order to prevent the lens sets from becoming eccentric or non-coaxial after the assembly to result in performance degradation.
A traditional zoom lens assembly has been disclosed in U.S. Pat. No. 6,049,432, as shown in FIG. 5 of the present specification. Meanwhile, a first lens group 90 and first lens holder 92 are constructed into a first lens set, and a second lens group 91 and second lens holder 93 are constructed into a second lens set. Both the first and second lens holders 92, 93 are mounted on a main frame 94. However the first and second lens holders 92, 93 mounted on the main frame 94, each uses only one spot to contact with a guide groove 95 for performing a telescopic movement, it may cause shakes while the lens holder is moving. Such a structure is not capable to completely ensuring that the first and second lens groups 90, 91 are moved oppositely along the same optical axis for all the time. Thus, it is hard to guarantee the optical performances of the zoom lens assembly. Besides, its fabricating method that the first and second lens groups 90, 91 are mounted on the main frame 94 separately will readily bring the fabricating quality more inaccuracies and degradation.
Understandably, it is necessary to provide a zoom lens assembly capable of assuring that each lens is coaxial with each other during moving oppositely or assembly.